The Obama administration is considering significant military backing for France’s drive against al-Qaeda-linked militants in Mali…. The loosely affiliated web of Malian militants in the country’s north includes members of al-Qaeda in the Islamic Maghreb (AQIM). But other fighters are longtime foes of the Malian government and pose no direct threat to U.S. interests …

Does the President have independent constitutional power to back the French in Mali? To the extent the President is contemplating direct military involvement (e.g., through the use of drones, as Professor Pearlstein suggests), it raises what I regard as two of the most difficult originalist questions in constitutional war powers. (If the question is only logistical and intelligence support, I assume there’s no constitutional problem so long as the President has discretionary funds available; those actions would come under his executive and commander-in-chief powers).

As to military action, let’s assume that the 2001 Authorization for Use of Military Force doesn’t apply, because the anti-government forces in Mali aren’t sufficiently connected with the 9/11 attacks; and let’s further assume that the conventional originalist reading of the declare war (which I share) is that the President must get Congress’ approval before initiating a “war.”

The first question in the Mali situation, then, is whether the U.S. can be at “war” with a non-state actor such as AQIM. In the post-9/11 debates, the George W. Bush administration argued that there could be a state of war against non-state actors, while many of Bush’s opponents said there could not be. Ironically, if the Bush opponents were right, then the President does not appear to need congressional approval to launch attacks against AQIM, or any other non-state actor, because that would not be “declar[ing] war.” Absent a limit from the declare-war clause, the President’s independent authority as commander-in-chief and holder of the executive power would be sufficient. (Even if the Constitution requires the President to use military force only in compliance with international law, the consent of the Mali government should take care of international law objections).

But as I’ve noted previously, the original materials on war and non-state actors are somewhat inconclusive. (See 69 U. Chicago Law Review 1543, 1611-12 & n. 254). Blackstone said that nations could (indeed, were obligated to) “declare war” on pirates, the leading non-state actors of the eighteenth century. Some international law writing, though, seemed to use “war” to mean conflict among sovereigns. The specific question of the application of the declare war clause to conflicts with non-state actors does not seem to have come up in the drafting, ratifying or immediate post-ratification periods. (Some people regard the various conflicts with the “Barbary Pirates” of the late eighteenth- and early nineteenth centuries as precedents, but that’s not right: these so-called pirates were under the control of the sovereign rulers of North African states such as Algiers and Tripoli.) My view is that the original materials marginally favor a requirement of congressional approval, but the matter hasn’t been exhaustively investigated (to my knowledge).

A second question might arise from the attack on the Algerian gas facility (on which details remain sketchy). Suppose (as seems likely) AQIM or other Mali-based insurgents attacked the facility and that Americans were targeted in the attack. Would that give the President independent authority to use military force against the attackers?

It’s broadly agreed that the President does have independent constitutional authority to respond to attacks on the United States, but there are two separate difficulties with finding that authority here. First, is an attack on U.S. civilians overseas sufficient to create a state of war between the U.S. and the attackers? Again the original materials are limited and ambiguous, but there is a case to be made that war was understood to be triggered only by attacks on territory or military forces. Attacks on civilians might violate international law and thus give just cause for war, in an eighteenth-century conception, but they did not appear to create war in themselves. This view would leave it to Congress to decide whether to respond to such attacks with warfare (although it might leave the President with a more limited power to conduct a rescue).

Second, in responding to an attack, is the President limited to immediate defensive measures, or may he counterattack against the attackers? This is another close question that I’ve debated with Professor Saikrishna Prakash (see here); my answer is that the President’s response is not limited, but the opposing argument is substantial. Thus one might suppose that even if the attack in Algeria created a war between the U.S. and AQIM, the President could not independently go beyond defending Americans in Algeria.

So in sum, I think (as an original matter) the President needs congressional approval to join the fight in Mali, because a war against a non-state actor is a war in the constitutional sense. The attack on U.S. civilians in Algeria probably isn’t enough to support an independent presidential war power because it wasn’t an attack on the United States. But (unlike the intervention in Libya, which I think clearly required congressional approval under the Constitution’s original understanding), the questions here are very difficult ones. And if you think there can't be "war" against non-state actors, there shouldn't be any constitutional problem with the President launching an attack on his own authority.